Messages in this thread | | | Date | Mon, 3 Apr 2023 11:57:21 +0530 | Subject | Re: [PATCH net-next 2/2] net: ethernet: ti: am65-cpsw: Enable USXGMII mode for J784S4 CPSW9G | From | Siddharth Vadapalli <> |
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Hello Russell,
On 31/03/23 19:16, Siddharth Vadapalli wrote: > > > On 31-03-2023 16:42, Russell King (Oracle) wrote: >> On Fri, Mar 31, 2023 at 04:23:16PM +0530, Siddharth Vadapalli wrote: >>> >>> >>> On 31/03/23 15:16, Russell King (Oracle) wrote: >>>> On Fri, Mar 31, 2023 at 02:55:56PM +0530, Siddharth Vadapalli wrote: >>>>> Russell, >>>>> >>>>> On 31/03/23 13:54, Russell King (Oracle) wrote: >>>>>> On Fri, Mar 31, 2023 at 01:35:10PM +0530, Siddharth Vadapalli wrote: >>>>>>> Hello Russell, >>>>>>> >>>>>>> Thank you for reviewing the patch. >>>>>>> >>>>>>> On 31/03/23 13:27, Russell King (Oracle) wrote: >>>>>>>> On Fri, Mar 31, 2023 at 12:21:10PM +0530, Siddharth Vadapalli wrote: >>>>>>>>> TI's J784S4 SoC supports USXGMII mode. Add USXGMII mode to the >>>>>>>>> extra_modes member of the J784S4 SoC data. Additionally, configure the >>>>>>>>> MAC Control register for supporting USXGMII mode. Also, for USXGMII >>>>>>>>> mode, include MAC_5000FD in the "mac_capabilities" member of struct >>>>>>>>> "phylink_config". >>>>>>>> >>>>>>>> I don't think TI "get" phylink at all... >>>>>>>> >>>>>>>>> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c >>>>>>>>> index 4b4d06199b45..ab33e6fe5b1a 100644 >>>>>>>>> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c >>>>>>>>> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c >>>>>>>>> @@ -1555,6 +1555,8 @@ static void am65_cpsw_nuss_mac_link_up(struct phylink_config *config, struct phy >>>>>>>>> mac_control |= CPSW_SL_CTL_GIG; >>>>>>>>> if (interface == PHY_INTERFACE_MODE_SGMII) >>>>>>>>> mac_control |= CPSW_SL_CTL_EXT_EN; >>>>>>>>> + if (interface == PHY_INTERFACE_MODE_USXGMII) >>>>>>>>> + mac_control |= CPSW_SL_CTL_XGIG | CPSW_SL_CTL_XGMII_EN; >>>>>>>> >>>>>>>> The configuration of the interface mode should *not* happen in >>>>>>>> mac_link_up(), but should happen in e.g. mac_config(). >>>>>>> >>>>>>> I will move all the interface mode associated configurations to mac_config() in >>>>>>> the v2 series. >>>>>> >>>>>> Looking at the whole of mac_link_up(), could you please describe what >>>>>> effect these bits are having: >>>>>> >>>>>> CPSW_SL_CTL_GIG >>>>>> CPSW_SL_CTL_EXT_EN >>>>>> CPSW_SL_CTL_IFCTL_A >>>>> >>>>> CPSW_SL_CTL_GIG corresponds to enabling Gigabit mode (full duplex only). >>>>> CPSW_SL_CTL_EXT_EN when set enables in-band mode of operation and when cleared >>>>> enables forced mode of operation. >>>>> CPSW_SL_CTL_IFCTL_A is used to set the RMII link speed (0=10 mbps, 1=100 mbps). >>>> >>>> Okay, so I would do in mac_link_up(): >>>> >>>> /* RMII needs to be manually configured for 10/100Mbps */ >>>> if (interface == PHY_INTERFACE_MODE_RMII && speed == SPEED_100) >>>> mac_control |= CPSW_SL_CTL_IFCTL_A; >>>> >>>> if (speed == SPEED_1000) >>>> mac_control |= CPSW_SL_CTL_GIG; >>>> if (duplex) >>>> mac_control |= CPSW_SL_CTL_FULLDUPLEX; >>>> >>>> I would also make mac_link_up() do a read-modify-write operation to >>>> only affect the bits that it is changing. >>> >>> This is the current implementation except for the SGMII mode associated >>> operation that I had recently added. I will fix that. Also, the >>> cpsw_sl_ctl_set() function which writes the mac_control value performs a read >>> modify write operation. >>> >>>> >>>> Now, for SGMII, I would move setting CPSW_SL_CTL_EXT_EN to mac_config() >>>> to enable in-band mode - don't we want in-band mode enabled all the >>>> time while in SGMII mode so the PHY gets the response from the MAC? >>> >>> Thank you for pointing it out. I will move that to mac_config(). >>> >>>> >>>> Lastly, for RGMII at 10Mbps, you seem to suggest that you need RGMII >>>> in-band mode enabled for that - but if you need RGMII in-band for >>>> 10Mbps, wouldn't it make sense for the other speeds as well? If so, >>>> wouldn't that mean that CPSW_SL_CTL_EXT_EN can always be set for >>>> RGMII no matter what speed is being used? >>> >>> The CPSW MAC does not support forced mode at 10 Mbps RGMII. For this reason, if >>> RGMII 10 Mbps is requested, it is set to in-band mode. >> >> What I'm saying is that if we have in-band signalling that is reliable >> for a particular interface mode, why not always use it, rather than >> singling out one specific speed as an exception? Does it not work in >> 100Mbps and 1Gbps?
While the CPSW MAC supports RGMII in-band status operation, the link partner might not support it. I have also observed that forced mode is preferred to in-band mode as implemented for another driver: commit ade64eb5be9768e40c90ecb01295416abb2ddbac net: dsa: microchip: Disable RGMII in-band status on KSZ9893
and in the mail thread at: https://lore.kernel.org/netdev/20200905160647.GJ3164319@lunn.ch/ based on Andrew's suggestion, using forced mode appears to be better.
Additionally, I have verified that switching to in-band status causes a regression. Thus, I will prefer keeping it in forced mode for 100 and 1000 Mbps RGMII mode which is the existing implementation in the driver. Please let me know.
Regards, Siddharth.
> > In-band RGMII is supported for speeds of 10, 100 and 1000 Mbps. > Unfortunately, I am not aware of the reason why RGMII at speeds 100 and > 1000 Mbps was implemented in the driver in forced mode. As suggested by > you, I will work on implementing it in in-band mode for all speeds and > verify that it works, following which I will post the v2 of this series, > with the following changes based on your feedback: > 1. All interface mode specific configuration will be moved to mac_config(). > 2. Since CPSW MAC supports USXGMII mode, MAC_5000FD will be added to the > list of mac_capabilites unconditionally, unlike the current implementation. > 3. In-band mode of operation will be enabled for all interface modes by > default. > > Regards, > Siddharth.
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